Spin-polarized scanning tunneling microscopy has been applied to study non-collinear spin textures of a Mn monolayer on a four-fold symmetric W(001) substrate revealing a zero-field spin spiral ground state and two different types of rotational domain walls. With an applied magnetic field of 9 T, we observe a coexistence of the spin spiral and the skyrmion phase, even though a previous theoretical study reported that the phase transition occurs at 18 T. The skyrmions show a roughly hexagonal arrangement despite the square lattice symmetry of the W(001) substrate. Based on a reduced set of energy parameters, we are able to describe the experimental findings and to analyze the topological properties of the rotational domain walls.
@article{arxiv.2201.10702,
title = {Nanoscale Skyrmions on a Square Atomic Lattice},
author = {Reiner Brüning and André Kubetzka and Kirsten von Bergmann and Elena Y. Vedmedenko and Roland Wiesendanger},
journal= {arXiv preprint arXiv:2201.10702},
year = {2022}
}